Polyaxial pedicle screw having provisional fastening means

ABSTRACT

A polyaxial pedicle screw includes a screwed shaft section for anchoring the pedicle screw in a vertebra, on one axial end of which a shaft head is configured which is coupled in a rotating and/or pivoting manner as well as in a tensile-force transmitting manner to a receiving sleeve for a longitudinal support. The receiving sleeve has a fastening means for selective positional fastening of the receiving sleeve with respect to the shaft section, the fastening means at least consisting of an inlay/pin mounted in the receiving sleeve and acting on the shaft head, and a locking element acting on the inlay/pin. The inlay/pin is configured with attachment points or engagement elements, which are not covered or overlapped by the locking element, for the provisional introduction of a compressive force on the inlay/pin parallel to the locking element.

RELATED APPLICATIONS

This application is the national phase of International Application No.PCT/EP2012/064207, filed Jul. 19, 2012, which claims the benefit ofpriority of German Application No. DE 10 2011 053 295.1, filed Sep. 6,2011, both applications being incorporated by reference herein as if setforth in their entireties, for all purposes.

FIELD

The present invention relates generally to a polyaxial pedicle screw,and more specifically to a polyaxial pedicle screw havingprovisional/temporary fastening means, a helping means/tool for theprovisional fastening of the polyaxial pedicle screw and also astabilization system featuring a pedicle screw according to theinvention, the helping means according to the invention and alsopreferably a longitudinal member.

BACKGROUND

Pedicle screws are used principally for the dorsal stabilization of thespinal column in the case of fractures, tumours, infections, deformitiesand degenerative instabilities by means of a transpedicular screwfixing. Pedicle screws are thereby placed in the pedicles of eachadjacent vertebrae, whereupon an angularly-stable connection is createdbetween the pedicle screws which are arranged axially above each otherand an axially extending longitudinal member or bar. The pedicle screwsand longitudinal member thereby form a vertebra stabilization system.

For this purpose, a pedicle screw generally has an axial, shaft-shapedexternally threaded portion to which a so-called tulip is connected onthe screw head side. This forms constructively a U-shaped longitudinallyslotted/tunneled receiving sleeve with internal thread, wherein the twolongitudinal slots lying radially opposite each other each define a slotgap of predetermined gap width. The longitudinal member is transverselyinserted in the longitudinal slots which run parallel to each other, andfixed by means of a locking element, for example a grub screw orthreaded nut, which is screwed into the internal thread.

In principle two basic types of pedicle screw are distinguished, namelymonoaxial and polyaxial pedicle screws. In the case of a monoaxialpedicle screw, the externally threaded portion or shaft and the tulipare integrally formed with each other such that they are basicallyfixedly connected to each other, for example welded or soldered. Bycontrast a polyaxial pedicle screw has, as a separate shaft member, amanufactured externally threaded portion having a mostly spherical or(semi-)spherical screw head which is encompassed relatively pivotablyand at the same time grasped from behind by the sleeve-shaped tulip, inthe transition region between head and shaft. In this way, after sinkingof the externally threaded portion in the pedicle channel of a vertebra,the tulip can be pivoted and/or turned relative to the shaft so as toobtain a desired position and orientation which is essentiallyindependent of the orientation of the shaft. In this way the undercutprevents the tulip from being able to be pulled off from the shaft head.Subsequently the tulip is positionally fixed to the screw head by meansof the grub screw in the case of a temporarily fixed bar (one-screwprinciple) or though an additional screw/nut (multi-screw principle).

Pedicle screws are put in place in the pedicle channel of a vertebra oranchored through screwing, by a surgeon. In doing so the operator alignsthe screws on the basis of the orientation of the pedicle channel. Whenthe screws are set, the above mentioned longitudinal member or bar ofthe correct length is selected, and optionally its longitudinalcurvature is adjusted to the pedicle screws and its respective positionis also adjusted. The longitudinal member should in addition be placedin the tulips of the pedicle screws.

The polyaxial pedicle screws distinguish themselves henceforth in thatthe tulip/receiving sleeve is at first movably placed with respect tothe screw shaft such that the receiving sleeve can take on a differentorientation from the shaft. This makes it easier for the surgeon tolaterally insert/guide the longitudinal member in the receiving sleeve.When the surge is satisfied with the seating of the longitudinal memberand the receiving sleeve, he locks the pedicle screw by means of thelocking element, preferably by means of the grub screw (in principlealso termed set screw of any configuration).

The polyaxial locking (positional fixing of the receiving sleeve withrespect to the shaft) as well as the clamping of the longitudinal memberare locked upon tightening of the set screw in a single assembly step inthe case of the above-mentioned one-screw principle.

In the case of polyaxial screws it is generally not possible during theimplanting procedure to introduce forces from the receiving sleeve tothe vertebra due to the mobility (link) between the screw shaft and thereceiving sleeve, in order to manipulate them for example. However thisis required in particular with repositioning manoeuvres in the case offractures or spondylolisthesis and partly with compressions ordistractions. For this purpose therefore the monoaxial pedicle screwsare used, whereby the receiving sleeve is rigid with the screw shaft.However these monoaxial pedicle screws have the disadvantage that thelongitudinal member can only with difficulty be laterally introducedinto the tulip/receiving sleeve of several monoaxial pedicle screws.

A polyaxial pedicle screw according to the above mentioned one-screwprinciple is known from the prior art, for example according to EP 2 301458 A1, consisting of a shaft member having external thread andspherical head as well as a U-shaped longitudinally slotted receivingsleeve (tulip) for a longitudinal support/bar. The receiving sleeve hasan internal thread in the axial region towards the opening of thelongitudinal slots, in which a grub screw can be screwed, and a radiallyinwardly oriented circumferential projection or land in the axial regionup to the respective slot base. Furthermore a type of piston or inlay isinserted in the receiving sleeve by means of a snap ring and in this waysecured against falling out.

For the assembly of the polyaxial pedicle screw known from EP 2 301 458A1, the receiving sleeve is first passed from the distal end (the endlying opposite the shaft head) of the shaft member over this shaftmember until the radial internal land of the receiving sleeve butsagainst the shaft head (on its under side). Subsequently the inlay ispushed into the receiving sleeve (i.e. on the upper side of the shafthead) such that the spring ring which is arranged circumferentiallybetween receiving sleeve and inlay snaps into correspondingcircumferential grooves on the inlay and on the receiving sleeve, andaxially holds both components together. The shaft head is thereforearranged between the land of the receiving sleeve and the inlay (i.e.underneath the inlay).

As soon as the pedicle screw is screwed into a vertebra and fixedlyanchored into it, a longitudinal member is introduced into the U-shaped(double) slot of the receiving sleeve (above the inlay), wherein thereceiving sleeve can turn and pivot relative to the anchored shaftmember. In this way it is possible for an operator to adjust thereceiving sleeve to correspond to the orientation of the longitudinalmember. As soon as the suitable relative position of the receivingsleeve is set, the grub screw is screwed into the receiving sleeve untilit locates the longitudinal member against the inlay and presses thisfurther in the axial direction of the receiving sleeve against the shafthead. In this way the entire pedicle screw/longitudinal member system(vertebra-stabilization system) can be fixed/locked in the set positionby tightening the single grub screw (locking element).

US 2008/02155100 A1 discloses for example a polyaxial pedicle screwaccording to the above mentioned multi-screw principle. This pediclescrew also has a shaft-shaped externally threaded portion having anintegral shaft head at a proximal end of the shaft. The shaft head isfreely rotatably and pivotably surrounded by a receiving sleeve, inwhich an internal thread is also configured and which comprises twoU-shaped longitudinal slots which lie opposite each other, for alongitudinal member.

A piston/inlay is axially movably inserted in the receiving sleeve,which likewise comprises a U-shaped longitudinal slot with theapproximate slot width dimension of the longitudinal slots in thereceiving sleeve. The flanks that occur here at the U-shapedlongitudinal slot of the inlay are elongated in the axial direction suchthat they protrude over a bar/longitudinal member transversely insertedin it. In other words the length of the flanks of the inlay is largerthan the diameter of the transversely inserted bar/longitudinal member.

In order to assemble the pedicle screw known from US 2008/02155100 A1,the receiving sleeve/tulip is passed over the shaft in a known manneruntil this axially bears on the shaft head (on the underside) in apivotable and rotatable manner. Subsequently the inlay (above the shafthead) is introduced into the receiving sleeve and its U-shaped slotaligned corresponding to the U-shaped slots in the receiving sleeve.After a longitudinal member/bar has been introduced into the U-shapedslot of the inlay (and inevitably here also into the slots of thereceiving sleeve), a first screw (screw sleeve), preferably a grub screwwhich was previously screwed into the internal thread of the receivingsleeve, is further tightened in order to press the inlay directlyagainst the shaft head and thus to fix the position of the receivingsleeve relative to the shaft. The longitudinal member however remainsinitially uninfluenced by the first screw, i.e. not fixed. In thisassembly state it is possible to apply an adjusting force via thereceiving sleeve to the vertebra.

The first screw is likewise sleeve-shaped and has an internal threadinto which a second screw (grub screw) is screwed. The longitudinalmember is now fixed in the inlay by means of this second screw, in whichthe second screw is rotated relative to the first screw and pressesdirectly against the bar in order to clamp said bar in the inlay. Inthis way the polyaxiality of the pedicle screw is locked and thereforethe longitudinal member is also fastened.

In the case of many pedicle screws according to the above mentionedconstruction, the fastening means/locking elements (screws) areessentially self-lockingly executed in order not to risk an undesiredloosening of the longitudinal member from the pedicle screws afterimplanting. In addition the fixing forces between pedicle screw andlongitudinal member are considerable because the entire system mustwithstand large loads without the set positional relationship betweenshaft, sleeve and longitudinal member being allowed to change. Itfollows that the clamping forces between the shaft head and thereceiving sleeve are likewise very high such that the frictional fitwhich forms in-between does not frequently come loose even when thefastening means is released. These requirements however also causeproblems during the implanting procedure.

-   -   As long as the receiving sleeve is not fixedly (by frictional        fit) connected with the shaft head, an adjusting force cannot be        transmitted via this receiving sleeve to the vertebra. In other        words, in the case of a polyaxial pedicle screw according to the        one-screw principle for example, a longitudinal member would        first have to be inserted and then the locking element,        preferably the grub screw, would have to be tightened in order        to be able to finally exert an adjusting force on the vertebra.        This however would not be technically sensible.    -   If an operator first of all has tightened the locking element        (for example the grub screw) with force and there might arise        afterwards the need of a post-adjustment, the positional        relationship fixed in this way is not modifiable again, or only        with great difficulty. Expressed in other words, for this        purpose the operator would have to release again, against their        self-locking effect, the grub screw(s) which have been tightened        with great force, without releasing or even breaking the        externally threaded portion which is already anchored in the        vertebra. Even if the grub screw can be released without        problems, a possible self-locking frictional fit is configured        between the shaft head and the receiving sleeve. This could be        released only through significant force effort (impacts on the        receiving sleeve, etc.), even in the case of a released grub        screw. Furthermore the locking element's self-locking effect is        possibly impaired due to its subsequent loosening, such that the        operability of the pedicle screw is no longer ensured.

To this extent, it would be advantageous in principle if thepolyaxiality is only provisionally fixable in particular in the case ofthe one-screw principle, in order to be able to at least temporarily andindependently lock the polyaxiality and the bar/longitudinal member. Inother words, it would be useful in the case of a polyaxial pediclescrew, also one according to the one-screw principle, to fix by means ofa special helping means to be used temporarily only the polyaxialitywithout the bar being fixed. This would have the advantage that now alsothe polyaxial pedicle screw would be suited to transmit, beforefastening the longitudinal member, correspondingly high forces to thevertebra for its manipulation during the implanting procedure withoutthe inner structure of the pedicle screw becoming significantly morecomplicated.

It should be noted at this point that the term “provisional”, inparticular in view of the invention described below, should notnecessarily mean only a light fitting/seizing of the shaft head, ratherit is understood in particular to mean such a locking measure which istemporarily used and also whose achievable locking properties such asthe clamping force on the shaft head etc. thoroughly correspond to thepermanent locking means and can at least approach or even exceed this.Expressed in other words the “provisional” locking means should bedimensioned such that it causes a locking of the receiving sleeve at theshaft head corresponding to the permanent locking element. In this caseof an optional subsequent loosening of the frictional fit in accordancewith the prior art, it would be possible only though considerable forceexertion, however there would be at least the possibility of vertebralreadjustment before fastening the longitudinal member. Alternatively, itwould also be desirable to dimension the “provisional” locking meanssuch that sufficient adjusting forces are transmittable on the vertebraby means of the polyaxial pedicle screw, wherein the frictional fitachieved here between shaft head and receiving sleeve is releasableagain.

However the polyaxial pedicle screws according to the described priorart prove themselves to be unfavourable. Therefore in particular in thecase of the one-screw principle the polyaxiality can be locked only whenthe longitudinal member sits (not yet fixed) in its end position. Aninserting of the longitudinal member after the locking of thepolyaxiality is actually not possible or is only very difficult andwould have as a prerequisite a clearly more complicated construction ofthe pedicle screw.

SUMMARY

In light of the above described problems, it is an object of theinvention to increase the functionality a polyaxial pedicle screw, inparticular by combining the benefits of a monoaxial pedicle screw withthose of a polyaxial pedicle screw. It is an object to allow themanipulability of a vertebra via the polyaxial pedicle screw (accordingto any execution principle) without the inserting of the longitudinalmember into the tulip becoming unduly difficult. Furthermore thepolyaxial pedicle screw should not have a (substantially) morecomplicated construction than the prior art.

The stated object is solved by a polyaxial pedicle screw havingprovisional/temporary fastening means (in the sense of the abovedefinition) according to claim 1, a helping means/tool for theprovisional fastening (in the sense of the above definition) of thepolyaxial pedicle screw as well as a stabilization system consisting ofthe pedicle screw according to the invention and the helping meansaccording to the invention. Advantageous further developments of theinvention are substantially the object of the dependent claims.

The basic idea of the invention is essentially based on causing theprovisional/temporary fixing (locking) of the polyaxiality by means ofan external helping means, which, parallel to the actual (permanent)locking element of the polyaxial pedicle screw, acts (preferably withcomparable force) on the inlay and the receiving sleeve in order to biasthese against each other and thereby clamp the shaft head which isarranged between inlay and receiving sleeve (in accordance with theactual locking element). The inlay and the receiving sleeve areconsequently provided/equipped with engagement elements for the helpingmeans, with which the helping means respectively engages (withforce-locking fit), in order to apply a corresponding biasing force onthe elements concerned (inlay and receiving sleeve). The engagementelement at the inlay is in addition prepared for the application of acompressive force and the engagement element on the receiving sleeve isprepared for the application of a tensile force.

Expressed in other words the (external) helping means according to theinvention can be designed such that, with its temporary use as describedabove, it at times replaces or simulates the actual locking element withreference to the fastening of the polyaxiality, and creates a frictionalfit between shaft head and receiving sleeve, which, depending on thedesired setting, is bigger or marginally smaller than the frictional fitachieved through the permanent locking element. This means thereforethat the term “temporary” should not be understood to the effect thatthe frictional fit achieved through the helping means is necessarilyreleasable again, rather that the helping means for the provisionalcreation of the (releasable or no longer releasable) frictional fit isdeployed parallel to the permanent locking element temporarily.

Constructively the above-mentioned basic idea is essentially implementedby the inlay being formed such that it projects or is exposed at leastin portions radially over the employed locking element, whereby at theseradial portions which are not covered/overlapped by the locking element,attachment points occur for the introduction of a compressive force onthe inlay parallel to the actual locking element. Conversely thereceiving sleeve is configured/provided with undercuts which areformed/suited for the external introduction of a tensile force.

More specifically the polyaxial pedicle screw according to the inventionhas a screwed shaft section for anchoring the pedicle screw in avertebra, on one axial end of which a (spherical or semi-spherical)shaft head is configured. The shaft head is coupled in a rotating and/orpivoting manner with a receiving sleeve for a longitudinal support,wherein the receiving sleeve comprises a fastening means for theselective positional fastening of the receiving sleeve with respect tothe shaft section. The fastening means has an inlay which is mounted inthe receiving sleeve and acts on the shaft head, and a locking elementacting on the inlay, whereby the inlay is biasable against the shafthead and thereby the shaft head clamps (by frictional fit) between theinlay and the receiving sleeve which engages behind the shaft head (withform-locking fit). According to a first aspect of the invention, theinlay is configured/provided with attachment points or engagementelements, which are not covered or overlapped by the locking element,for the introduction of a (provisional/temporary) compressive force onthe inlay parallel to the locking element, preferably using a separatetool-like helping means.

Another aspect of the invention provides that the inlay is formed suchthat it projects or is exposed, at least in portions, radially over thelocking element, whereby the attachment points occur (for the separatehelping means) at these radial portions which are not covered oroverlapped by the locking element.

It can be advantageous when the inlay has an outline deviating from acircle, preferably an oval outline, at least at one axial (inlay)portion whereby those outline portions with large diameter protruderadially over the locking element and contain the attachment points.Alternatively here it is also possible to form radially projecting lugsat the inlay, or even to give a many-cornered profile to the inlay,whereby outline areas occur which protrude radially over the lockingelement which is preferably a screw/grub screw. In this way a separatehelping means/tool for the provisional/temporary fastening at least ofthe polyaxiality can be guided along to the (not yet locked) lockingelement and be brought into axial compressive engagement with the inlay.

Preferably the attachment points are marked by axial centring holeswhich serve for the receiving and placement of an external helping meansfor the application of pressure to the inlay. Thus the helping meanscannot slide off from the inlay and the projecting outline portions ofthe inlay can be designed to be relatively small.

In order to be able to exert a sufficiently large provisional/temporaryfixing force on the inlay (comparable to the actual locking element) itis advantageous when the inlay and the receiving sleeve are biasableagainst each other by means of the separate helping means. To this aimthe receiving sleeve may be configured or provided with at least oneengagement element via which an external provisional tensile forceparallel to the locking element can be applied to the receiving sleeve.Preferably the engagement element is an undercut which furtherpreferably is formed on the external sleeve-side of the receivingsleeve. This has the advantage of the radial displacement of that memberof the helping means which should apply a compressive force on theinlay, from that member with which a (counter) tensile force is exertedon the receiving sleeve. Thereby both members of the helping means canbe placed almost one inside the other, whereby this becomes very compactand also stable.

Another aspect of the invention relates to a helping means for theprovisional/temporary fastening of the polyaxiality of a pedicle screwsuch as the one described above. The helping means, provided as aseparate tool, has a first member preferably in the form of a plungerfor coming into pressing engagement with the attachment points providedat the inlay and a second member, preferably a pulling member which ismovable relative to, preferably in opposition to, the first member andhas a latching or clasping means which can be brought into pullingengagement with the receiving sleeve, preferably at its engagementelement. Preferably the pulling member is a sleeve surrounding theplunger wherein, at an axial end of the sleeve, radially inwardlyprotruding latching projections, hooks or ledges are formed in order tomake releasable latching engagement with the receiving sleeve,preferably at the receiving sleeve's engagement elements. Furthermorethe sleeve is preferably operatively connected with the plunger on anaxial end section lying opposite the latching protrusions via acoupling. This coupling causes a compressive force from the plunger tobe converted into a tensile force from the surrounding sleeve wherebythere arises a provisional/temporary closed flow of forces betweeninlay, shaft head, receiving sleeve and separate helping means. Theanchoring of the pedicle screw in the vertebra remains unaffected fromthis.

Another aspect of the invention relates to a stabilization system thathas the following components:

-   -   a polyaxial pedicle screw at least consisting of a screwed shaft        having shaft head surrounded and grasped from behind by a        receiving sleeve in which is mounted an inlay biasable against        the shaft head by means of a locking element which is preferably        screwable into the receiving sleeve and    -   a manually operatable helping means, preferably of a tool type,        which has a first member for the selective        (provisional/temporary) application of pressure to the inlay and        a second member for the selective (provisional/temporary)        tensile loading of the receiving sleeve (as counter-reaction to        the provisional application of pressure), which is parallel to        the locking element in each case.

Preferably the stabilization system of the invention further has

-   -   a longitudinal member which is insertable in a transverse slot        of the receiving sleeve, wherein at least the first member and        preferably also the second member of the helping means is/are        designed (preferably having U-shaped longitudinal slots) so that        it/they engage/s around the longitudinal member such that the        longitudinal member can then still be introduced when the        helping means is already set and activated.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below on the basis of apreferred exemplary embodiment with reference to the accompanyingdrawings.

FIG. 1 shows the perspective view of a polyaxial pedicle screw accordingto a preferred exemplary embodiment of the invention,

FIG. 2 shows the pedicle screw of FIG. 1 in top view,

FIG. 3 shows a partially broken-line view of the pedicle screw of FIG.1,

FIG. 4 shows the perspective view of a stabilization system according toa preferred exemplary embodiment of the invention consisting of thepedicle screw according to FIGS. 1 to 3 and a tool-like external helpingmeans,

FIG. 5 shows a further perspective view of the stabilization systemaccording to the invention with helping means in working position,

FIG. 6 shows a perspective view of the stabilization system according tothe invention with helping means in working position and insertedlongitudinal member,

FIG. 7 shows a perspective view of the stabilization system according tothe invention according to FIG. 6, additionally with locking element inplace,

FIG. 8 shows the stabilization system in the readily assembled state andwith helping means removed,

FIG. 9a-9b shows a perspective view of the helping means according tothe invention without coupling, and

FIG. 10 shows a side view of the helping means according to FIG. 9,having a coupling in the form of a shaft-nut.

DETAILED DESCRIPTION

The polyaxial pedicle screw 1 shown in FIGS. 1 to 3 according to thepreferred exemplary embodiment of the invention has a shaft or anchor 2provided with an external thread, wherein at the proximal end of theshaft or anchor 2 a preferably spherical or at least semi-sphericalshaft head 4 is formed or moulded. A tool engagement 6, for example foran “Imbus” key or a cross-headed screwdriver etc., is incorporated inthe shaft head 4, in order to be able to screw the shaft 2 into thepedicle channel of a vertebra (not shown).

As can be seen from FIG. 3, the shaft head 4 forms at its transitionregion to the screwed shaft/shaft section 2 an undercut acting in theaxial direction. This occurs in the present case by the shaft headdiameter being chosen to be larger than the shaft diameter.Alternatively, it would also be conceivable to set the shaft head 4apart from the remaining screwed shaft section 2 by means of a turnedgroove (not shown) at the proximal end section of the shaft 2.

According to FIG. 3 the shaft head 4 is grasped by a receiving sleeve 8which (at first) is rotatably and pivotably held by the shaft head 4.

Specifically the receiving sleeve 8 has a cylindrical sleeve body 10open on both sides, whose sleeve wall is slotted in a U-shape on theproximal end face, whereby there occurs a passing transverse groove(slot) 12 running essentially vertically to the sleeve axis. Thereceiving sleeve 8 is configured with an internal thread in the axialregion towards the open side of the U-shaped slot 12, which according toFIG. 2 extends approximately until an axial mid-section of the sleeve 8.In the opposite lying axial region (e.g. at the axial distal end) of thesleeve 8, i.e. behind the slot base of the U-shaped slot 12, thereceiving sleeve 8 is configured with a circumferential inner radialprojection/land 14 which narrows the sleeve's inner diameter at thefront end and therefore represents an undercut. The diameter of theinner radial protrusion 14 is thereby sized such that it is marginallybigger than the diameter of the screwed shaft section 2 but smaller thanthe diameter of the shaft head 4.

Furthermore the inner diameter of the sleeve 8 or of the sleeve body 10is marginally larger than the diameter of the shaft head 4. By means ofthe U-shaped longitudinal slots 12 there occur two flanks lying radiallyopposite each other in the sleeve body 10, wherein engagement elements11 are moulded or formed at each of the sleeve body's respective outershell side. Here it presently concerns, for each flank, two axiallyspaced notches/pockets which form undercuts acting in the axialdirection. Alternative to this, but equally possible, is to formstrip-shaped protrusions on the external sleeve side of the flanks,which form the engagement elements 11. Basically therefore any form ofengagement element is conceivable as long as an axial (provisional)tensile force can be applied in this way in the direction away from theshaft head 4 to the receiving sleeve 8.

A stamp-shaped power transfer member (inlay) 16 is put in place/insertedin the receiving sleeve 8. This inlay 16 is essentially formed by meansof an inlay sleeve which lies on top of the shaft head 4 at one of itsend faces. The other end face of the inlay sleeve (or simply inlay) 16is widened into a flange-shaped collar 18 which in top view according toFIG. 2 is oval or rectangularly shaped, and in side view (see alsoFIG. 1) is formed into a concave channel/basin. (Blind) holes 20 areaxially incorporated at the corners of the rectangle, wherein the holes20 represent force introduction or attachment points for a tool-likeexternal/separate helping means.

The receiving sleeve 8 and the inlay 16 are constructively adapted foreach other such that the inlay 16 is displaceable at least over apredetermined distance in the receiving sleeve 6. Furthermore theinlay/pin 16 is inserted into the receiving sleeve 8 such that the basinwhich is formed/bulged at the inlay 16 on its end face diametrallyconnects both of the parallel U-shaped slots 12 with each other at thecollar 18 and thus forms the support for an inserted longitudinalmember, as is described in the following.

The operation of the polyaxial pedicle screw according to the preferredexemplary embodiment of the invention is described below in particularwith reference to FIG. 8.

Consequently the pedicle screw 1 according to the invention is fixedlyanchored at its screwed shaft 2 into the pedicle channel of a vertebra.A locking element preferably in the form of a grub screw 22 is screwedinto the internal thread of the receiving sleeve 8, whereby the U-shapedslot(s) 12 is/are closed off at the receiving sleeve's 8 end face facingaway from the shaft. In the lateral passage opening which is formed inthis way, a longitudinal member 24 is inserted which longitudinallyconnects pedicle screws of different (axially adjacent) vertebra. Thegrub screw 22 is tightened so that the polyaxiality of the pedicle screw1, i.e. the relative position between shaft 2 and receiving sleeve 8, isfixedly locked as desired and at the same time the longitudinal member24 is fixedly clamped between the inlay 16 and the grub screw 22. Inthis locked state the screw force of the grub screw 22 is thereforetransmitted via the longitudinal member 24 and the inlay 16 to the shafthead 4 and clamps it (by frictional fit) between the inlay 16 and theinner radial projection 14 of the receiving sleeve 8.

The internal thread in the sleeve body 10 is sized such that it causes aself-locking. This means that the grub screw 22 can be released againonly with considerable force. In addition, the receiving sleeve 8 ismovable before the tightening of the grub screw 22 with respect to theshaft 2 such that no adjusting forces can be manually applied to theshaft 2 via the receiving sleeve 8, for example in order to change theposition of the relevant vertebra.

To solve this problem an additional helping means 30 according to FIGS.4 to 7 is provided.

This helping means 30 basically consists of a first member (plunger) 32,which can be brought into (form-locking) engagement with the inlay 16,and a second member (tension sleeve) 34 which can be brought into(form-locking) engagement with the receiving sleeve 8.

Specifically the first member 32 of the helping means 30 according toFIG. 4 is a plunger or piston, at one (distal) end face of which areformed a number of cones/spikes whose size and placement correspond tothe (blind) holes 20 in the inlay 16. These are arranged due to thecircular external outline of the collar 18 outside the footprint of thepreferably circular locking element 22 such that the plunger 32 canstill be brought into contact with the (blind) holes 20 for aprovisional/temporary compressive force application of the inlay 16 whenthe locking element 22 is already screwed into the receiving sleeve 8and is marginally supported via the inserted longitudinal member 24against the inlay 16.

In the simplest case the plunger 32 is sleeve-shaped and completelysurrounds the receiving sleeve 8. A slightly more complicated designaccording to FIG. 4 provides that the plunger 32 has two diametral axialgrooves 32 a at its distal end portion, which are sized so that both ofthe flanks of the receiving sleeve 8 can be axially introduced into itwith substantially an exact fit. In this case therefore the meandiameter of the plunger 32 may approximately correspond to the meandiameter of the receiving sleeve 8. In addition the plunger 32 isadditionally longitudinally slotted in a U-shape in accordance with theslots 12 in the receiving sleeve 8 such that these slots 12 are notclosed off from the plunger 32 when in the set state, and thus alongitudinal member can be introduced also when the helping means isattached in the longitudinal slot.

According to FIG. 5 the tension sleeve 34 is arranged movably around andrelative to the plunger 32, wherein optionally anothercentral/intermediate sleeve (not further depicted) between plunger 32and tension sleeve 34 can be arranged. The tension sleeve 34 has at itsdistal end section a number of latching elements (not further shown)which with the notches/indentations 11 can be brought into releasablelatching engagement with the flanks of the sleeve body 10. Finally thetension sleeve 34 is coupled at its opposite lying (proximal) endsection with the plunger 32, such that both members are movable andthereby biasable via a coupling, as shown as an example in FIGS. 9 and10.

For example the coupling may be a shaft-nut which is rotatable butaxially fixedly placed at the tension sleeve 34 and can be screwinglyengaged with the plunger 32. If consequently the shaft-nut is manuallyrotated, plunger 32 and tension sleeve 34 rotate relatively to eachother in opposite directions. In this way the plunger 32 can be moved,by means of suitable manual turning of the shaft-nut, in the directiontowards the inlay 16 and at the same time the tension sleeve 34 can bemoved in the direction away from the inlay 16. In this case thereceiving sleeve 8 can be provisionally/temporarily tightened withrespect to the inlay 16 via the described helping means 30, wherein theshaft head 4 arranged in between is likewise provisionally/temporarilyclamped.

Alternatively, for this purpose, it is also possible to form the tensionsleeve 34 according to FIG. 9 with an external thread 34 a at itsproximal end section facing away from the pedicle screw, wherein thetension sleeve 34 is provided at this proximal end section with at leastone longitudinal slot 34 b (preferably two diametral longitudinalslots). In this case the plunger 32 has radially projecting drive pins32 b at its proximal end, which drive pins 32 b protrude radiallyoutwardly through the longitudinal slots 34 b to the tension sleeve 34.According to FIG. 10 a shaft-nut 35 is screwed onto the external thread34 a of the tension sleeve 34, which shaft-nut 35 is in engagement withthe drive pins 32 b of the plunger 32. If now the shaft-nut 35 isrotated on the tension sleeve 34, a relative movement between theplunger 32 and the tension sleeve 34 is thus created.

Finally it should be pointed out at this point that other coupling formsare also conceivable which create a relative movement between plunger 32and tension sleeve 34 by use of a lever effect or a gear reductionmeans.

The operation of the helping means 30 according to the invention isdescribed more closely in the following, with reference to FIGS. 4 to 7.

Consequently, according to FIG. 4, the plunger 32 is first guided intothe (blind) holes 20 of the inlay/pin 16, wherein the flanks arelongitudinally guided on the sleeve body 10 in the axial grooves 32 a ofthe plunger 32. In this relative position the slots 12 at the receivingsleeve 8 overlap with the U-shaped slot in the plunger 32, whereby asort of lateral window is formed.

Subsequently the tension sleeve 34 is guided over the plunger 32 andlatched with its latching protrusions in the notches 11 at the receivingsleeve 8. The tension sleeve 34, as clearly recognizable in FIG. 5, isalso provided with U-shaped slots in accordance with the slot in theplunger 32, such that the lateral window furthermore remains open whenthe tension sleeve 34 is pulled over.

As soon as the helping means 30 is mounted on the inlay 16 and islatched with the receiving sleeve 8, the coupling (shaft-nut) 35, shownfor example in FIGS. 9 and 10, and with it the shaft head 4 isprovisionally/temporarily tensioned. According to the type of coupling,provisional preload forces are hereby achievable, which are the same asthe preload forces of the actual locking element of the pedicle screw.

In this state a force from the helping means 30 via the receiving sleeve8 can now be transmitted to the shaft 2, for example to adjust thevertebra. Subsequently the longitudinal member 24 is inserted accordingto FIG. 6 into the lateral window and the locking element, preferablythe grub screw 22 already inserted in advance, is tightened, without thehelping means 30 having to be removed in advance. With the tightening ofthe grub screw 22, the polyaxiality is finally locked such that thehelping means 30 can be subsequently removed. In this way the assemblyprocedure is completed.

Finally the present invention is again summarised as follows:

Disclosed is a polyaxial pedicle screw 1 having a screwed shaft section2 for anchoring the pedicle screw 1 in a vertebra, on one axial end ofwhich a shaft head 4 is configured which is coupled in a rotating and/orpivoting manner as well as in a tensile force transmitting manner to areceiving sleeve 8 for a longitudinal support 24. The receiving sleeve 8has a fastening means for selectively fixing the position of thereceiving sleeve 8 with respect to the shaft section 2, said fasteningmeans at least consisting of an inlay/bolt 16 mounted in the receivingsleeve 8 and acting on the shaft head 4 and a locking element 22 actingon the inlay 16. The inlay 16 is designed having attachment points orengagement elements 20, which are not covered or overlapped, for theprovisional/temporary introduction of a pressure force on the inlay 16parallel to the locking element 22. The attachment points or engagementelements 20 are configured as attachment points having form-locking fitor engagement elements 20 having form-locking fit.

Furthermore a tool-like helping means 30 is disclosed which can beattached (parallel to the locking element 22) with the inlay/pin 16 atits attachment points 20 for a provisional/temporary application ofcompressive force, and with the receiving sleeve 8 preferably at itsengagement elements 11 for a provisional/temporary application oftensile force. Preferably the helping means 30 has two members, namely apressing member 32 and a pulling member 34 which are coupled togethersuch that a provisional application of pressure to the inlay 16 via oneof the members necessarily leads to a tensile loading of the receivingsleeve 8 via the other member for achieving a balance of forces.Optionally the tool-like helping means 30 is provided at least partiallyas a disposable product. In particular the pressing member 32 shouldpreferably be configured as a disposable member because it getscomparatively near to the vertebra of the patient and therefore canbecome contaminated with bodily fluids. In principle it is convenient ifthe entire helping means 30 is disposed of after its single use.

Finally a stabilization system according to the invention consists ofthe polyaxial pedicle screw 1, the helping means 30 and preferably alongitudinal member 24 which is inserted and fixedly clamped in thereceiving sleeve 8.

The invention claimed is:
 1. A polyaxial pedicle screw having a screwedshaft section for anchoring the pedicle screw in a vertebra, wherein ashaft head is configured at an axial end of the shaft section, saidshaft head being pivotably and/or rotatingly coupled to a receivingsleeve, wherein the receiving sleeve comprises a fastening means forselective positional fastening of the receiving sleeve with respect tothe shaft section, said fastening means at least consisting of an inlaymounted in the receiving sleeve and acting on the shaft head, and alocking element acting on the inlay and screwed directly into thereceiving sleeve, wherein the inlay is configured with inlay engagementelements having form-locking fit, which are not covered or overlapped bythe locking element, for the introduction of a provisional compressiveforce parallel to the locking element on the inlay, wherein the inlay isformed such that it projects or is exposed, at least in portions,radially over the locking element, whereby the inlay engagement elementsoccur at these radial portions which are not covered or overlapped bythe locking element, and wherein the inlay engagement elements aremarked by axial centering holes which serve for the receiving andplacement of an external helping means for the provisional applicationof pressure to the inlay.
 2. The polyaxial pedicle screw according toclaim 1, wherein the inlay has an outline deviating from a circle, atleast at one axial portion whereby outline portions of large diameterprotrude radially over the locking element and contain the inlayengagement elements.
 3. The polyaxial pedicle screw according to claim1, wherein the inlay is formed essentially by an inlay sleeve, one endface of which is widened to a flange-like, oval or rectangular collar.4. The polyaxial pedicle screw according to claim 3, wherein radiallyprojecting lugs are configured at the inlay at the corners of therectangular collar, wherein the radially projecting lugs constitute theinlay engagement elements.
 5. The polyaxial pedicle screw according toclaim 1, wherein the receiving sleeve comprises a cylindrical sleevebody open on both sides whose sleeve wall is slotted in a U-shapestarting from a proximal end face, whereby there occur two flanks lyingradially opposite each other, wherein the inlay engagement elements arelocated between the two flanks.
 6. The polyaxial pedicle screw accordingto claim 5, wherein the inlay diametrally connects both of the U-shapedslots in the sleeve body.
 7. The polyaxial pedicle screw according toclaim 1, wherein the receiving sleeve is configured or provided with atleast one receiving sleeve engagement element via which an externalprovisional tensile force parallel to the locking element can be appliedto the receiving sleeve.
 8. The polyaxial pedicle screw according toclaim 7, wherein the engagement element forms an undercut on an externalsleeve-side of the receiving sleeve.